1. Field of the Invention
This invention relates to a piezoelectric switch and in particular to a piezoelectric switch having a circuit with a piezoelectric element incorporated in the switch housing which provides a pulse output, and an oscillating signal to the piezoelectric element for producing audible feedback when the piezoelectric element is activated by mechanical stress.
2. DESCRIPTION OF RELATED ART
Piezoelectric switches in the prior art have not incorporated an audible feedback using a piezoelectric element within the switch housing for detection by an operator activating the switch. If such a switch did exist, it could be used in current piezoelectric switch applications which do not have tactile or audio feedback.
The piezoelectric switch produces a momentary pulse; it is an all-electronic switch having no contact arcing or bounce and no movable parts or mechanical wear. Such a switch is a normally-open momentary, single pole, single throw (SPST).
In U.S. Pat. No. 4,028,502, issued Jun. 7, 1997 to Moricca et al., and assigned to Inventive Industries, Inc., an apparatus is described for providing auditory and tactile recognition of a light signal associated with a line-selector pushbutton of a multi-line telephone instrument. A photo cell senses a light signal and an oscillator generates a sine wave voltage which is amplified and applied to excite a piezoelectric crystal into vibration in response to activation of the photo cell. An auxiliary pushbutton is disposed in alignment with the line selector pushbutton so that manual depression of the auxiliary pushbutton actuates the line selector pushbutton. Vibration of the crystal in response to the light signal acts upon an auxiliary pushbutton to import the vibration thereto so that the presence of the light signal is sensed by a blind person by vibration of the auxiliary pushbutton.
In U.S. Pat. No. 4,430,595, issued Feb. 7, 1984 to Nakasone et al. and assigned to Toko Kabushiki Kaisha of Japan, a piezoelectric pushbutton switch is described comprising a housing with terminals embodied in four corners, a printed circuit board, a disk-shaped piezoelectric plate polarized in the direction of thickness and having its upper surface bonded to a conductive plate, a domed-shaped metal spring placed on the conductive plate, and a plunger placed on the metal spring 8. A cover has a through-hole into which the plunger is inserted. When the spring is bent, the operator can feel a clicking motion through the plunger and the finger. The piezoelectric plate floats free of the housing by being supported by a protruding piece on the flexible printed circuit board.
In U.S. Pat. No. 4,642,433, issued Feb. 10, 1987, to Taneo Murata, and assigned to Alps Electric Company, Ltd. of Japan a pushbutton switch with aural confirmation of operation is described. The switch used in a keyboard gives a tactile feel to the finger of the operator like a clicking and at the same time produces a clicking sound. The switch comprises a casing, a membrane switching device in the casing, a stem, a contact spring and a leaf spring which produces a clicking sound.
In U.S. Pat. No. 5,636,729, issued Jun. 10, 1997 to Richard Wiciel, a piezoelectric switch with a lighted push-button is described. The switch comprises a light-transmissive member having a first surface accessible to a tactile input and a second surface opposite the first surface, a case for mounting the member, a piezoelectric crystal mounted to the case and having a contact area, a light source disposed in the case, a spacer for transmitting the tactile input to the crystal causing the crystal to provide an electrical response to the tactile input to an electronic circuit.